The present invention relates to low-cost improvement of performance of multiple radio wireless access points. It relates to combinations of an antenna and one or more of a filter or an active components such as a power amplifier, low noise amplifier, switching diode or RF phase shifter (with a plurality of antennas), connected to the antenna connector of a radio component.
Multiple radio wireless LAN (WLAN) access points are emerging product category. For instance, Linksys has announced that it will soon ship a universal wireless access point (WAP55AG) that includes two radios and supports three standards for wireless communications: 802.11a, 802.11b. and 802.11g. Support for multiple wireless communications standards is becoming increasingly important in the unlicensed radio spectrum. For instance, Bluetooth and 802.11 standards operate in the unlicensed spectrum at approximately 2.4 and 5.25 gigahertz. Support for multiple communications standards is important as wireless communication speeds increase from 2 to 11 to 54 Mbps. The evolution of standards has led to such suggestions as programmable filter systems in which components are reconfigurable for a variety of air interface standards. See, U.S. Patent App. No. US 2002/0183013 A1, “Programmable Radio Frequency Sub-System with Integrated Antennas and Filters and Wireless Communication Device Using Same”, published 5 Dec. 2002. Inevitably, such grand designs with integration of radio components and antenna components are relatively expensive to implement and better suited to portable devices than to access points or base stations.
One issue with use of multiple radios in a compact access point is the effect of noise from one radio on reception by another radio. See, European Patent App. No. EP 1 294 048 A2, entitled “information Device Incorporating an Integrated Antenna for Wireless Communication”, published 19 Mar. 2003, at columns 1-2. Low-cost power amplifiers create a certain noise level across a broad spectrum. This is illustrated in FIG. 1, by signal curve 101 and noise curve 102. Two typical approaches are to improve the radio by adding on-board components or to increase the separation distance between antennas. The first approach increases the expense of the access point. The other approach increases the size.
At a practical, manufacturing level, access point technology involves contract manufacturing of commodities. Radios used by different manufacturers of access points are or may become standardized, interchangeable commodities. A manufactured access point, illustrated by FIG. 2, may include a motherboard 201, plug-in radio modules 202-203 and antennas 204-205. The motherboards and radio modules may be built to specification, according to designs of commodity manufacturers and not to designs of the manufacturers who brand the access points. In the future, the radios may be integrated on the motherboard by the commodity manufacturers.
Given the anticipated popularity of multiple radio wireless access points, an opportunity arises for methods and devices that improve performance at a modest cost, while taking advantage of commodity components.